Electron-emissive films are known in the art. For example, it is known to use a diamond film as an electron source. Emissive diamond films are typically formed by chemical vapor deposition. However, the uniformity of the electron emission of these prior art films is often poor.
It is also known in the art to fabricate an electron-emissive film by applying diamond particles to a metal foil. An example of this prior art method is described in U.S. Pat. No. 5,648,699, entitled "Field Emission Devices Employing Improved Emitters on Metal Foil and Methods for Making Such Devices", by Jin et al. Jin et al describe the deposition of emissive particles by utilizing a wet spray-coating method, electrophoretic deposition, or sprinkling through a fine sieve. Jin et al teach that the step for depositing the emissive particles is distinct from the step for bonding them to the metal foil. Jin et al further teach that use of a wet spray-coating method requires mixing the particles with a liquid medium and further requires a drying step subsequent to the deposition of the liquid mixture.
However, emissive particles in liquid solution may form aggregates, which result in poor uniformity of emission properties of the final film. Furthermore, if the drying step results in incomplete drying, the emission properties of the film can be compromised.
Another method for fabricating an electron-emissive film is described in published international application number WO 96/42101, entitled "Electron Source and Applications of the Same", by DeHeer et al, having an international filing date of Jun. 11, 1996. DeHeer et al teach a method for fabricating a carbon nanotube film, which includes the steps of mixing a nanotube-containing carbonaceous material in a liquid solvent, filtering the suspension, drying the filtered solids, and then transferring the filtered solids to a Teflon film. However, it is known that nanotubes dissolved in a liquid solvent tend to aggregate and agglomerate. A film formed from such aggregates tends to have poor uniformity of electron emission properties. Furthermore, the multiplicity of steps results in added costs and decreased yield.
Accordingly, there exists a need for a method for fabricating an electron-emissive film, which overcomes at least these shortcomings of the prior art.